구차니의 잡동사니 모음

# ll /etc/systemd/system/basic.target.wants

합계 0

lrwxrwxrwx. 1 root root 41  1월 16  2017 firewalld.service -> /usr/lib/systemd/system/firewalld.service

lrwxrwxrwx. 1 root root 47  1월 16  2017 gitlab-runsvdir.service -> /usr/lib/systemd/system/gitlab-runsvdir.service

lrwxrwxrwx. 1 root root 41  1월 16  2017 microcode.service -> /usr/lib/systemd/system/microcode.service 

# systemctl status gitlab-runsvdir

● gitlab-runsvdir.service - GitLab Runit supervision process

   Loaded: loaded (/usr/lib/systemd/system/gitlab-runsvdir.service; enabled; vendor preset: disabled)

   Active: active (running) since 화 2019-01-22 12:42:45 KST; 3 weeks 3 days ago

 Main PID: 620 (runsvdir)

   CGroup: /system.slice/gitlab-runsvdir.service

           ├─  620 runsvdir -P /opt/gitlab/service log: ....................................................................

...

           ├─18710 sleep 3000

           └─18789 sleep 1

 1월 22 12:42:45 localhost.localdomain systemd[1]: Started GitLab Runit supervision process.

 1월 22 12:42:45 localhost.localdomain systemd[1]: Starting GitLab Runit supervision process... 

# virsh dumpxml GuestID > guest.xml

# virsh create configuration_file.xml 

create FILE [--console] [--paused] [--autodestroy]

Create a domain from an XML <file>. An easy way to create the XML <file> is to use the dumpxml command to obtain the definition of a pre-existing guest. The domain will be paused if the --paused option is used and supported by the driver; otherwise it will be running. If --console is requested, attach to the console after creation. If --autodestroy is requested, then the guest will be automatically destroyed when virsh closes its connection to libvirt, or otherwise exits.

Example

virsh dumpxml <domain> > domain.xml

vi domain.xml (or make changes with your other text editor)

virsh create domain.xml

define FILE

Define a domain from an XML <file>. The domain definition is registered but not started. If domain is already running, the changes will take effect on the next boot. 

$ sudo yum install kvm libvirt 

$ sudo yum install virt-manager

       --sparse=WHEN

              control creation of sparse files. See below

        By default, sparse SOURCE files are detected by a crude heuristic and the corresponding DEST file is made sparse as well.  That is the behavior selected by --sparse=auto.  Specify --sparse=always to create a sparse DEST file whenever the SOURCE file contains a long enough sequence of zero bytes.  Use --sparse=never to inhibit creation of sparse files.

       -S, --sparse

              Handle sparse files efficiently.  Some files in the file system may have segments which were actually never written (quite often these are database files created by such systems as DBM).  When given this option, tar attempts to determine if the file is sparse prior to archiving it, and if so, to reduce the resulting archive size by not dumping empty parts of the file. 

$ tar -cvfS test_spar.tar 123123.qcow2

$ tar -S -cvf test_spar.tar 123123.qcow2 

$ ll

-rw-------. 1 root root   9665380352 Aug  8  2018 123123.qcow2

-rw-r--r--. 1 root root      1484800 Feb 14 18:10 test_spar.tar

-rw-r--r--. 1 root root   9665382400 Feb 14 18:09 test.tar

 To have tar attempt to recognize the holes in a file, use `--sparse' (`-S'). 

Advantages

The advantage of sparse files is that storage is only allocated when actually needed: disk space is saved, and large files can be created even if there is insufficient free space on the file system.

Disadvantages

Disadvantages are that sparse files may become fragmented; file system free space reports may be misleading; filling up file systems containing sparse files can have unexpected effects; and copying a sparse file with a program that does not explicitly support them may copy the entire, uncompressed size of the file, including the sparse, mostly zero sections which are not on disk -- losing the benefits of the sparse property in the file. 

ls -s tells you the allocated size of the file, always a multiple of the allocation unit. ls -l tells the actual size. An easy way to test: 

$ man ls

       --block-size=SIZE

              scale sizes by SIZE before printing them; e.g., '--block-size=M'

              prints sizes in units of 1,048,576 bytes; see SIZE format below